The invention relates to a method of two-dimensional nuclear magnetic resonance (2-D NMR) correlation spectroscopy, wherein double quantum coherence (DQC) is excited.
Such a method is known, e.g., from A. Bax et al., J. Am. Chem. Soc. 1980, 102, p. 4849-4851 (compare Ref. 2).
Nuclear magnetic resonance (NMR) is a powerful tool for investigating the chemistry of a sample. NMR measures the reaction of the spins of the nuclei within the sample upon excitation with high frequency electromagnetic pulses.
2D NMR1 techniques are especially useful to identify spin correlations which in turn reflect the bonding or spatial topology of the molecule. For low abundance spins, the correlation information has been produced by exciting Double Quantum Coherence (DQC)2,3 which is subsequently reconverted following evolution by either a single pulse (of flip angle typically 45°, 60°, 90°, 120° or 135°), or alternatively by a cluster of pulses as in the 2D INADEQUATE CR sequence4-6. 2D INADEQUATE CR has been designed to provide the maximum sensitivity and results in transition selectivity in F2. These experiments result in spectra whose F1 frequencies are sums of the chemical shifts of each pair of coupled spins. COSY- or SECSY-type displays for 13C spin systems are also known in the literature7,8. These methods afford sub-optimal sensitivity, however, there being no transition selectivity.